The invention relates to an osteosynthetic aid for tubular bones. More specifically, the invention relates to a locking nail system as has become known for the fixation of fractures of tubular bones, particularly the femur, tibia or humerus. The basic principle is embodied in an elongate nail shank which has at least one cross-bore at each of its ends. The cross-bore is traversed by a bone screw or locking screw with which the nail shank is located in the bone in both the axial and rotational directions.
A peculiar problem in using locking nails of this type, e.g. for humeral head fractures, is posed by the postsurgical migration of the screws. Since the bone fragments may move or the bone is resorbed the bias which is produced while the locking nail is screwed in can be lost and, as a result, can cause the locking screw to come unscrewed.
When the locking nail is employed as a supracondylar nail it is known to pass a so-called tibial bolt through the condyles. It usually comprises a tibial bolt which has a relatively long shank and a threaded portion, and a tibial nut which is screwed onto the shank. The tibial nut can have a sleeve-shaped portion to allow a smooth shank to be formed between the nut and the head of the screw. If such a treatment is applied, also because bone elements are resorbed or fragments will shift, it might happen that it is no longer possible to sufficiently secure the location of the nail shank, i.e. it will migrate away sidewards, for example.